a study on infants, one of the characteristics measured was head circumference. The mean head circumference of 15 infants was 34.6 centimeters (cm). Complete parts (a) through (d) below. Click here to view Page 1 of the table of areas under the standard normal curve. Click here to view Page 2 of the table of areas under the standard normal curve. a. Assuming that head circumferences for infants are normally distributed with standard deviation 2.3 cm, determine a 95% confidence interval for the mean head circumference of all infants. The confidence interval for the mean head circumference of all infants is from cm to cm. (Round to one decimal place as needed.) b. Obtain the margin of error, E, for the confidence interval you found in part (a). The margin of error is cm. (Round to one decimal place as needed.) c. Explain the meaning of E in this context in terms of the accuracy of the estimate. Choose the correct answer below and fill in the answer box to complete your choice. (Round to one decimal place as needed.) O A. We can be 95% confident that the error made in estimating u by x is at most cm . O B. We can be 95% confident that the error made in estimating u by x is at least cm. O C. We can be 95% confident that the estimate of u by x is cm. O D. We can be 95% confident that the possible values of u are within cm of each other. d. Determine the sample size required to have a margin of error of 0.7 cm with a 99% confidence level. The required sample size is . (Round up to the nearest whole number.)